Analysis of MIMO radar ambiguity functions and implications on clear region

Multiple input multiple output (MIMO) radar offers the potential for improved performance over more traditional single input multiple output (SIMO) radar. MIMO radar operates by transmitting separable waveforms from multiple transmitters and the resulting radar echos are received by multiple receivers. While there is a great deal of literature discussing the benefits of MIMO techniques, a handful of publications discussing the limitations of MIMO radar techniques have appeared in the literature. Of particular interest is the work addressing the reduction of the clear area in range-Doppler space [2]. Using a particular form of the MIMO ambiguity function, it was shown for a MIMO radar transmitting N waveforms there is a reduction of the clear area by a factor of 1/N. In this paper, we repeat this analysis for the ambiguity function applicable to a coherent MIMO radar. We show the MIMO ambiguity function proposed in [2] does not fully capture some important features of coherent MIMO radar and differs from versions of the ambiguity function proposed by other authors. In the second half of this paper, we derive the MIMO ambiguity function for coded pulse train waveforms. In addition to the traditional narrowband assumption, we develop the MIMIO ambiguity function using the “start-and-hop” radar signal model.